Screw-cutting die.



R. W. ROELOFSON.

SCREW CUTTlNG DIE. APPLICATION FILED AUG.2I. 191s.

1,2439% Patented May1,1917.

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RICHARD W. ROELOFSON, GAL'I, ONTARIO, CANADA.

soaEw-ourrme DIE.

Specification of Letters Patent.

Patented May 1, 1917.

Application fi1ed'August21, 1916. Serial No. 116,158.

Improvements in Screw-Cutting Bios, of

which the following is a specification.

This invention relates to screw cutting dies in which a plurality of radially arranged chasers are employed, and my object is to provide means for easily and accurately adjusting the chasers to operate on stock of various diameters, and also means for automatically releasing the chasers from their work topreventthe tearing or spoiling of the threads which have been cut when the thread is finished and the die is rotated in a reverse direction to back it off. v

I attain my objects by means .of the constructions hereinafter described and illustrated in the accompanying drawings in which I Figure 1 is a plan view of myimproved die with the face plate removed;

Fig. 2 a longitudinal section of the same; and I Fig. 3 a perspective view of one of the pivots of the chasers. I

In the drawings like numerals of reference indicate corresponding parts in the dif ferent figures.

1 is the body of the die, either integral or built up. A plurality of radial slots 2 are formed therein. 3 are slotted pivots having their hearings in the body of the die and arranged so that their axes are intersected by the median planes of the slots 2. 4: are the chasers, which are adapted to slide in the slots in the pivots 3. These chasers, it will be noted, are not as wide as the slots, so that the chasers may rock with the pivots 3 as fulcrums. The extent of the rocking movement permitted the chasers is regulated by the stops 5, which are preferably formed as screws threaded into suitable holes in the body of the die and adapted to project through the sides of the slots 2 as shown particularly in Fig. 1. B suitably adjusting the stops 5 the extent of the rocking movement permitted each chaser can be accurately regulated.

The chasers are adjusted radially by means of the collet 6, which is screwed on the body 1 and has its inner surface beveled to engage the corresponding beveled ends which may be erly adjusted the point of of the chasers 4-. A look nut 7 is preferably provided to clamp the collet as adjusted. The collet tends only to press the chasers radially inward.

In order. to hold the chasers out against the collet I provide for each chaser a conepointed pin 8 set in a recess in the body of the die and normally pressed toward the chaser by means of a coil spring 9. Preferably each pin extends -axially through the lower end of the pivot 3 ofthe chaser as shown particularly in Fig. 2. The pin in this case is provided with the head 10 engaged by the spring. The cone points of these pins engage in similar shaped recesses 11 formed in the chasers. These recesses are so located that when the chasers are propeach pin is not pressed down to the bottom of the recess when the chaser is in the proper position. Each pin thus has a wedging action tending to force back its chaser against the collet 6.

I thus provide very accurate and reliable radial adjustment to the chasers so that they may be accurately set to cut a thread of the desired depth and to suit diflerent diameters of stock.

The rocking movement of each chaser, though only through a few thousandths of an inch, is of the utmost importance, since when the die is rotated in the reverse direction to back it of the finished thread, the chasers rock so as to free the cutting edges sufliciently from the cut thread so that they will turn back freely on the finished screw without tearing or spoiling the threads. When the die is rotated in the proper di rection to cut the thread, the chasers rock automatically under the frictional pressure to their proper cutting position. The stop screws 5 enable the extent of the release to be very accurately regulated.

What I claim as my invention is:

1. In a screw threading die, the combination of the die body; a plurality of radial chasers carried by said body and each pivotally mounted adjacent its cutting end; and stops limiting the rocking movement of each chaser in either direction.

2. In a screw threading die, the combination of the die body; a plurality of radial chasers carried by said body and each pivotally mounted adjacent its cutting end; and adjustable stops'limiting the rocking movement of each chaser in either direction.

3. In a screw threading die, the combination of the die body; :1 plurality of pivots mounted on said body and slotted for the passage of chasers; a plurality of radial chasers adapted to slide through said pivots, said pivots being normally adjacent the cutting edges of the chasers; and stops engageable by the chasers limiting the rocking movement of each chaser in either direction.

4. In a screw threading die, the combination of the die body; a plurality of pivots 5 arranged to slide radially; stops limiting the rocking movement of each chaser in either direction; and a collet threaded on the body adapted to adjust the chasers radially.

6. In a screw threading die, the combination of the die body; a plurality of radial chasers carried by said body and each pivotally mounted adjacent its cutting end and arranged to slide radially; stops limiting the rocking movement of each chaser in either direction; a collet threaded on the body adapted to adjust the chasers radially;

and a cone-pointed spring actuated pin engaging each chaser, the chaser-being provided with a coned recess for engagement by the point of the pin, the recess being positioned so that the pressure of the pin tends to retract the chaser from its work.

7. In a screw threading die, the combination of the die body; a plurality of radial chasers carried by said body and each pivotally mounted adjacent its cutting end; adjustable stops limiting the rocking movement of each chaser in either direction; and a cone-pointed spring actuated pin passing through the head of each pivot and engaging the corresponding chaser, the chaser being provided with a coned recess for engagement by the point of the pin, the recess being positioned so that the pressure of the pin tends to retract the chaser from its work. I

8. In a screw threading die, the combination of the die body; a plurality of radially movable chasers carried by said body; a collet threaded on the body adapted to adjust the chasers radially; and a conepointed spring actuated pin engaging each chaser, the chaser being provided with a coned recess for engagement by the point of the pin, the recess being positioned so that the pressure of the pin tends to retract the chaser from its work.

Signed at Galt, Ontario, this twelfth day of August, A. D. 1916.

R. W. ROELOFSON.

Witnesses:

J. B. Lone, G. MoELLwIN.

Gopies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

